1. Field of the Invention
The present invention relates to a musical tone control apparatus for an electronic musical instrument and, more particularly, to an apparatus for forming a nonlinear table to control a generation of musical tone in a sound source means comprising a delay feedback synthesis circuit for processing musical tone control data on the basis of a nonlinear table.
2. Description of the Prior Art
In an electronic musical instrument, arithmetic processing of a musical tone signal having a predetermined tone color, pitch, tone volume, or vibrato is performed by a sound source circuit on the basis of control input data to generate an electronic tone simulating that of an acoustic instrument, and the electronic tone is produced form a sound system.
As a conventional sound source circuit, a sound source using a so-called delay feedback type decay tone algorithm for inputting a nonlinear signal in a delay loop system including a delay circuit, and performing feedback arithmetic processing of the nonlinear signal to form a musical tone waveform signal is known (Japanese Patent Laid-Open Gezette No. Sho 63- 40199).
In an electronic tone forming apparatus using a delay feed back type musical tone waveform signal, a mechanical vibration system of an acoustic instrument such as a string of a bowed instrument and a tube of a wind instrument is physically simulated by an electrical circuit, and a nonlinear signal corresponding to movement of a contact between a bow or a string of a bowed instrument, or a reed or embouchure of a wind instrument, or a hammer of a percussion, a piano, or the like need only be inputted to the delay loop system, so that a tone of the wind instrument, the bowed instrument, or the percussion including a change in intensity level can be naturally and faithfully synthesized.
In the sound source as the electronic tone forming apparatus, nonlinear functions for obtaining nonlinear signals are stored in advance in, e.g., a ROM as a table, and a control circuit (CPU) performs arithmetic processing of control data of musical tone parameters, thus forming an electronic tone according to a given nonlinear function.
However, in the sound source of the conventional electronic musical instrument, since nonlinear function table is set in advance, and is stored in a circuit, a control range of electronic musical tones is limited to the characteristics of the nonlinear table, resulting in a limited electronic tone forming range.